Typical antiperspirant products use aluminum and aluminum-zirconium salts to prevent perspiration or reduce underarm sweat production. The degree of sweat reduction is directly related to the effectiveness of the antiperspirant salts. In general, aluminum and aluminum-zirconium antiperspirants of enhanced efficacy are those salts that reduce perspiration to a greater extent than do the analogous conventional salts. Aluminum or aluminum-zirconium antiperspirant salts of enhanced efficacy usually involve those actives that either have low metals to chloride ratios or higher HPLC Band III to Band II area ratio or both. Antiperspirant salts of enhanced efficacy at low metals to chloride ratios generally have lower pH values; products with lower pH tend to increase the irritancy potential of the actives. Also, antiperspirant salts of enhanced efficacy that have higher HPLC Band III (or peak 4) to Band II (or peak 3) ratio of at least 0.5 with at least 70% aluminum species present in Band III and Band II are not stable in solution form and their preparation is lengthy and not economical.
U.S. Pat. No. 6,375,937 B1 and U.S. Pat. No. 6,436,381 B1 disclose aluminum-zirconium antiperspirant salts at low metals to chloride ratios of 0.9 to 1.2 said to have increased efficacy in comparison with those salts having higher metals to chloride ratios. The process of making the salts however comprises a task that generally involves diluting, heating and cooling of the aluminum hydroxychloride solution, mixing with zirconium glycinate solution and spray drying the final solution. It should be noted also that aluminum-zirconium salts at low metals to chloride ratios are very acidic. Such salts, when formulated into antiperspirant products such as sticks, can cause skin irritation and degradation of the fragrance. Further, the sticks tend to become soft and develop an acidic odor over time, thus becoming aesthetically undesirable.
U.S. Pat. No. 6,726,901 B2 discloses an anhydrous antiperspirant composition containing aluminum-zirconium salt with low metals to chloride ratio. That reference mentions that it is possible to neutralize some of the acidity of the salt by adding a basic material to the aqueous solution during its manufacture. The antiperspirant efficacy of the salt, however, tends to decrease as the neutralization changes the properties of the antiperspirant salt. A stabilizing basic material is added separately in the formulation to prevent the degradation of the antiperspirant composition and to minimize acid odor so as not to diminish the efficacy of the salt. Four categories of stabilizing basic materials are mentioned: salts formed by a strong base and a weak acid; amino acids that are basic; salts formed by a strong base and an amino acid include calcium glycinate and strontium glycinate; and inorganic bases that are not soluble in water such as calcium oxide and strontium oxide. No distinction is made between the four classes, or within each of the four classes, in terms of effectiveness. Furthermore, in that disclosure the basic materials are introduced in the antiperspirant formulations. These materials are not introduced in the antiperspirant salts.
WO 97/48371 describes a topical formulation for reducing skin irritation that involves an aqueous soluble strontium cation. Strontium nitrate is selected as the anti-irritant salt component. While the formulation containing aqueous soluble strontium salt can be used in different products, no level of efficacy is apparent for that antiperspirant product.
U.S. Pat. No. 4,017,599 discloses an aluminum-zirconium antiperspirant composition buffered with an amino compound of alkaline and alkaline earth salts. In an Example, calcium glycinate is prepared by mixing glycine with calcium carbonate at elevated temperature, which is then reacted in-situ with aluminum hydroxybromide and zirconium hydroxybromide. When the same method is employed to generate calcium glycinate in-situ with aluminum hydroxychloride and zirconium hydroxychloride, solution gelling was observed upon heating.
U.S. Pat. No. 5,955,065 presents a topical antiperspirant composition comprising a dermatological acceptable anhydrous carrier vehicle having suspended an aluminum or an aluminum-zirconium antiperspirant salt and a water soluble calcium salt. This reference contains no disclosure of calcium salt being directly introduced to the antiperspirant active.
U.S. Pat. No. 6,042,816 describes a method of stabilizing an aqueous solution of enhanced efficacy aluminum-zirconium antiperspirant salt containing an effective amount of a water soluble calcium salt and an effective amount of a water soluble amino acid against rapid degradation of HPLC peak 4 (Band III) to peak 3 (Band II) ratio of the salt. The soluble salts are readily dissolved in water or in an aqueous solution of antiperspirant salt. As a soluble calcium salt, calcium chloride dihydrate is demonstrated in all the examples. It is clearly stated that only calcium provides the stabilization of enhanced efficacy antiperspirant salts. It does not teach the use of insoluble, strongly alkaline salts such as calcium oxide or strontium hydroxide. The aluminum salt used in the patent is ⅚ basic aluminum chlorohydrate (ACH) wherein the aluminum to chloride mole ratio is about 1.9:1 to 2.1:1.
U.S. Pat. No. 6,245,325 which a continuation-in-part of the continuation of the application resulting in above U.S. Pat. No. 6,042,816, broadens the compositional claims of U.S. Pat. No. 6,042,816 and as well as the composition application; however, the latter disclosure maintains the use of water soluble calcium compounds and does not move beyond the definition of a method of stabilizing an aqueous solution of enhanced efficacy aluminum-zirconium antiperspirant salt containing an effective amount of a soluble calcium salt and an effective amount of a water soluble amino acid against rapid degradation of HPLC peak 4 (Band III) to peak 3 (Band II) ratio of the salt.
U.S. Pat. No. 5,908,616 describes basic aluminum halides and nitrates having enhanced efficacy with aluminum to anion mole ratio of about 1.2 to about 1.8 and at a concentration of about 30%–40% by weight of anhydrous solid. The compositions have HPLC Band II of at least 50% and Band III of less than 20%. The composition, however, does not provide a higher HPLC Band III to Band II area ratio of at least 0.5.
Based on an overview of the known prior art it is apparent that it is highly desirable to provide aluminum and aluminum-zirconium salts of enhanced efficacy that are economical, to have the aluminum and aluminum-zirconium salts that have excellent skin aesthetics and that have the aluminum and aluminum-zirconium solutions which not only have enhanced efficacy, but are also stable.